Guatemala City, Guatemala (CNN) -- The death toll from the eruption of a volcano in Guatemala has risen to at least three people, an official said Friday.

Two villagers from El Bejucal and a reporter from CNN affiliate Noti 7 were killed as a result of Thursday's eruption of the Pacaya volcano, said David de Leon, a spokesman for the national disaster commission.

The three victims were crushed by rocks strewn by the volcano.

Pacaya, located about 18 miles (30 kilometers) south of Guatemala City, began spewing ash and soot Thursday evening.

Guatemalan President Alvaro Colom declared a state of calamity for 15 days and called for calm as the eruption spread ash over the capital, prompting evacuations and shutting down the city's international airport.

Four people were missing as evacuations continued, the president said.

At least 1,800 people have been placed in shelters after four villages near the volcano were evacuated, de Leon said.

The runway at La Aurora International Airport -- the third busiest airport in Central America in terms of passenger traffic -- was covered with ash and was closed Friday, Colom said.

About 25 percent of the airport's daily flights had to be diverted to alternative airports after La Aurora was closed Thursday evening, said Monica Monje with Civil Aeronautics.

The states of Guatemala, Escuintla and Sacatepequez were hardest hit. Classes were canceled Friday in Escuintla and Guatemala states, Colom said.

A slight rain that fell over the area mixed with the ash, hindering visibility.

"I was returning from the university," he said. "It was really hard to drive because the ash was coming down with a bit of rain, so it was kind of muddy and really hard to get off the windshield. I drove with my window open so I could see."

Said iReporter Josue Rendon: "The scene was chilling. All night, it was raining sand!"

The volcanic ash led to some traffic mishaps, Rendon said.

"The houses in Guatemala City were not damaged, but all the streets are filled with sand," he wrote in English. "Have been reported several traffic accidents due to skidding of cars."

Another iReporter expressed his concern. Luis Morales, 27, said he lives in a Guatemala City neighborhood called Villa Hermosa, about 10 miles from the volcano.

"I'm worried for all the families that remain at the volcano area," he said.

iReporters are CNN viewers who share their images and stories.

Pacaya had been dormant for a century until 1965, when it erupted again. It has been active since.

Its summit has an elevation of 8,373 feet (2,552 meters).

Pacaya was the first of two volcanoes to erupt in Latin American since Thursday.

Ecuador's Tungurahua volcano, which has erupted periodically since 1999, came to life again Friday. Residents of two nearby villages were evacuated, but there were no reports of deaths or injuries.